Several Foxes defenders stood off Carter who had space to deliver a 30-yard piledriver which flew into Paul Henderson's top right-hand corner.
Ironically, the only other time Preston had threatened was after just 30 seconds when Henderson had to be alert to block Craig Beattie's close-range shot.
The result left Leicester still seeking their first back-to-back wins of the season.
It also dragged the Foxes into the relegation mire with an encounter against table-topping Bristol City next up at the Walkers Stadium on Saturday.
Lee Hendrie, on loan from Sheffield United, impressed on his home debut with a steady flow of clever flicks and passes which would have been rewarded with a goal on 38 minutes, had not Simon Whaley just beaten him to Iain Hume's near-post cross.
The only other chance created by either side before the break came when Hume and Dudley Campbell combined for Richard Stearman to whip over a cross which eluded Andy Lonergan, but there was no Leicester player near to take advantage of the gaping goal.
Stephen Clemence was substituted by Joe Mattock on the hour mark to give Hendrie a central role as Leicester laboured to create chances.
After Patrick Kisnorbo had blazed wide Hendrie's half-cleared free-kick, referee Roger East made the first of a series of controversial decisions which left Ian Holloway and the home crowd seething.
First the official failed to spot Youl Mawene's clear backpass to his keeper. Then he ruled two efforts by substitute Matt Fryatt out for offside.
And deep into time added on the entire Leicester side were convinced that Stearman had bundled home a late, late leveller, only for the referee to disallow it for an infringement.